A conventional system for detecting a shape of an insertion portion of an endoscope may be equipped with a FBG (fiber sensor that detects distortion using an amount of wavelength shift). The conventional system has a configuration in which a cable extending from the endoscope is connected to an optical connector provided in a shape detection device which is separately configured from the endoscope, and thereby a light signal from the FBG sensor is transmitted to the shape detection device. Therefore, the shape detection device is equipped with a light source (tunable laser) and a detector.